AFBI develops carbon calculator for Northern Ireland dairy farms

AFBI Develops Carbon Calculator for Northern Ireland Dairy Farms

Greenhouse gas emissions from dairying

Increasing concerns about the impact of climate change have focused the attention of government and policy makers on the need to develop accurate estimates of greenhouse gas (GHG) emissions from key sectors. This is particularly true within the United Kingdom where the UK Climate Change Act requires an 80% reduction in GHG emissions by 2050, relative to 1990 emission levels. Achieving these ambitious reduction targets will require a significant effort across all sectors. Within the agricultural sector, dairying in particular makes a significant contribution to total GHG emissions, with the global dairy sector estimated to contribute 30% of total global agricultural emissions. This highlights the need for the dairy industry to accurately quantify its emissions, and to identify strategies by which these can be reduced.

BovIS carbon calculator for dairy farms

Through DARD and AgriSearch funding, AFBI has developed the BovIS carbon footprint calculator to assist the Northern Ireland dairy industry in demonstrating its low carbon footprint relative to other EU member states. This calculator has been independently verified against international standards (PAS 2050; International Dairy Federation), and also validated by comparing the GHG emissions generated by the calculator for nine NI farms, with those obtained from three other GHG calculators used in France and the Netherlands. Total GHG emissions and emissions per kilogram of milk were relatively similar across the four calculators, with individual farm variation captured accurately and consistently across all calculators. The verification and comparison provide confidence in the ability of the AFBI calculator to estimate GHG emissions for NI dairy farms, and in its ability to be an important tool in the development of mitigation strategies to reduce GHG emissions at farm level. Local dairy producers can use this calculator to estimate the quantity of GHG emissions per litre of milk produced. The easy-to-use calculator accounts for all activities within a farm that are sources of GHG emissions, such as emissions from rumen fermentation, manure management, fertiliser manufacture and application, and concentrate production and transportation. The calculator uses the latest research findings from AFBI and other national and international scientific studies.

How does it work?

The online calculator is available to all producers through the DARD Online service. Located with the suite of BovIS applications, users are guided through a user-friendly e-questionnaire. The information required relates to farm management and annual production, such as: land area for grass and cereal production, number of cows and heifers and milk production, concentrate input and grazing management, fertiliser input and manure management, and fuel and electricity used. For certain values that are difficult to produce, a range of default factors are provided by the application. The calculator produces a summary report which shows the emissions produced by each part of the farming system.  Through calculating their carbon footprint, producers can investigate ways to reduce the GHG emissions from their dairy enterprise. Figure 1 shows the footprint of a typical moderate concentrate input dairy herd in Northern Ireland.  The carbon footprint of this system was calculated to be 1085 g of CO2e/kg milk (blue bar in Figure 1), with over 50% coming as methane production from enteric fermentation. Fertiliser usage was the second largest source of emissions, particularly as this includes emissions during manufacturing and transport of fertiliser as well as losses on the farm.  The third highest source of GHG emissions was from manure, which was at a relatively similar level to the applied fertilizer. Carbon sequestration by permanent grassland offset approximately 18% of the GHG emissions produced by the farm (green bar in Figure 1) therefore reducing the overall footprint. Through understanding the farming system, potential GHG mitigation strategies can be explored. Using this moderate input farm as an example, reducing the age at first calving from 27 to 24 months of age reduces the overall dairy GHG footprint by 7%. This reduced footprint was a result of fewer heifers in total on the farm which also meant that less land, forage, fertiliser and concentrate was required.

‘Low Carbon’ credentials of Northern Ireland milk

The carbon footprint of dairy farms in Northern Ireland is appreciably lower than those of dairy farms in many other regions of Northwest Europe. In a major interregional study (DAIRYMAN INTERREG Project) involving 132 pilot dairy farms across 10 regions of Northwest Europe, average GHG emissions per unit ECM on Northern Ireland farms (0.97 kg CO2e/kg ECM) proved to be the second lowest, with highest emissions (>1.25 kg CO2e/kg ECM) from dairy farms in Wallonia, the Republic of Ireland and Luxembourg.

Efficiency key to minimising the carbon footprint of milk production

Using the BovIS GHG calculator on data collected at AFBI Hillsborough clearly demonstrates that production efficiency, rather than the specific production system itself, is the key determinant of the carbon footprint of milk production. A high concentrate input total confinement system was compared to a medium concentrate input grazing system involving either Holstein-Friesian or cross-bred (Jersey × Holstein-Friesian) cows. The grazing cows were offered 1 kg of concentrate/day during a 199-day grazing period and grass silage and concentrates when indoors. The other group of cows were confined throughout the lactation and offered grass silage and concentrates. Full-lactation concentrate intakes were 791 and 2,905 kg/cow for the grazing and confined cows, respectively. Total emissions allocated to milk production were 36% greater for the confined cows, due to higher emissions related to dietary concentrate supplementation, manure management and enteric fermentation. In contrast, total emissions per kg of energy corrected milk (ECM) were similar with both systems (1.04 and 1.03 kg CO2e/kg ECM, respectively). Total emissions from Holstein-Friesian cows, when housed indoors, were 9% higher than from the cross-bred cows, reflecting higher milk yields, intakes and replacement rates with the former. In contrast, emissions per kg of ECM were 3% lower with Holstein-Friesian cows than with the cross-bred cows, when confined, a consequence of the poorer response of crossbred cows to concentrate supplementation. Generally, the results demonstrate that the carbon footprint of contrasting milk production systems is very similar, provided the most efficient breed is used within the system.

Summary

Reducing greenhouse gas emissions involves understanding the relationship between soils, livestock, environment and farm management, but fortunately lower GHG emissions are generally linked to improved production efficiency and profitability. Therefore producing milk efficiently will have positive effects on the GHG emissions from the Northern Ireland dairy sector. By routinely using the AFBI developed BovIS calculator producers can now:

1. calculate the quantity of GHG emitted from their farm per litre of milk produced
2. examine the effect of adopting management changes on the carbon footprint of their farm.

Notes to editors: 

AFBI carries out high-quality technology research and development, statutory, analytical, and diagnostic testing functions for DARD and other Government departments, public bodies and commercial companies.

AFBI's Vision is “Scientific excellence in Northern Ireland … serving the world”.

 All media enquiries to AFBI Press Office 

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